sothpaw2

Hi Everyone,

I hate to bring this up again but I am running out of ideas.

My C5Z's ignition is cutting out completely in/just after left hand hard turns. It only happens in high G situations, after the apex, when you are still cornering but giving it gas. It almost always happens only in 3rd gear (I suspect because of additional torque available) but running hard at VIR I did get it down the hill after T10 in 4th gear when I entered T10 at a hot clip. It never happens if you enter a corner slow (say rain speed) and don't get on the gas to hard while in the corner after apex)

When it happens I'm losing the HUD and all the gages go to zero. I won't swear but I think the clock radio is still on but I think the message screen is off--it's just like you turned the car off w/the key.
I saw a puff of smoke at the right front wheel at VIR--this reminded me that a fellow driver approached me about that at Summit last year--but it was a right turn.

It's very intermittent--the car restarts immediately by turn of the key--at Summit I did this once without leaving the racing surface while on the stort straight at low speed.

What makes this a real PIA is that I can't duplicate it other than on track. I tried in a nice parking lot the other day--got it hot to 248 oil, when in left turns, applied throttle until way after I was oversteering.
Did this in 1st gear though due to enclosed space.

So my questions are:

1. Would HP tuners or some other software I could obtain have a data sampling rate fast enough to catch this? Would it monitor enough signals to be of any use?

2. Do you think this could be due to the heat of the trans and it's movement? I had the trans out for rebuild 3 years ago. None other than Danny Popp(I really enjoyed meeting Dan!) looked under there at VIR and he suggested looking at that. My mechanic though looked at the other stuff Danny suggested and much more (Junction blocks, fuse box area, harness traced in engine area, etc grounds on eng. block, spices on frame rails, etc)but said to get a good look at the harness there would mean removing the torque tube etc and I know at that point that I may as well get a clutch. He also was kind enough to pull the PCM out at my request, heat the hell out of it with a heat gun, and shake the hell out of it w/ car running--to no avail.

Any advice/experience greatly appreciated!!

Thanks

Andy

96CollectorSport

It seems like the entire electical system is cutting out if the engine is cutting out and the dash goes dead. So I would guess that it would be a major power source grounding out or a ground being disconnected.

What kind of battery are you running in the car and how old is it?

The reason I ask is because the factory wet cell batteries have plates that sit in the battery acid, if you have a plate that is loose and contacting another plate you would have a dead short inside the battery which could cause something like that. If it's old I'd suggest a Optima dry cell, no plates to come loose. Just a big guess, swapping out batteries is an easy thing to try.

Electical gremlins are always a complete pain, but the fact that this is killing the engine and the dash would make me think that it's a main (not just a simple ground).

sothpaw2

Hilariously when this happened last fall at Summit I had a GM lead acid battery in the car. The first thing I did after that session was double check and tighten some more on the battery cable screws. Next fill gas tank to brim. Still happened next session.

Because of the harsh winter that battery went south and I put an Optima in there in January 2010. Electrical gremlin still happened at VIR in March. So battery is out.

W/regards to the dash, I'm 100% certain the HUD goes and the needles to zero. I don't specifically recall looking at my oil temp gage readout but I think it was gone.

If it helps any--this happens fast--there's no warning. Neither instructor (3) had any idea what happened. That's why I think the clock & such was still there--we would have noticed it by now.

davidfarmer

Maybe your ignition switch is bad....... Grounds are always problemati, but you'd have to be losing a primary ground for the entire system to die

sothpaw2

C5 tech posters are suggesting that because I have keys (not tons but maybe 9 plus the fob in addition to the chip key plus a small) that I have worn out the switch with taking too many turns.

Does this sound familiar to anyone here? I would not have guessed it was that fragile. People have keys especially if this is the daily driver.

0C5stein

Check for possible trouble codes and Comm errors. My guess is that a harness is rubbing on a sharp piece of metal and under hard cornering, it is grounding out. A code might give you an idea where to begin your search.

sothpaw2

Unfortunately there are no codes! Ever! I thought it was something like this last fall and my mechanic (and I before him) looked at the wiring in detail. Grounds good and no signs of chaffing. But you can't see inside the looms. So he moved them a but so if it was rubbing through a loom it would rub a new place.

That didn't work.

gkmccready

I haven't heard this one since the, um, mid-80s, I think. But I quit carrying all my keys together on a large keychain... largely to keep less crap in my pockets every day, but I saw no harm in reducing the load on the column.

Interesting that a left turn would actually try to pull away from the column and a right would cause them to rest against it, though, eh?

96CollectorSport

There are several people that have had ignition switch issues with C5's the ignition switch is only $55 and that would make sense for the engine and the dash to go out at the same time.

Kinda like I said before this has to be a major ground or major short to shut down the engine and the dash. If it was a ground or a wire rubbing somewhere it would have to be pretty large to shut down the entire electrical system and more than likely you would see (or smell) something burnt where it's happening.

The only smaller wires that could shut the car down would be around the ignition switch. That wouldn't be a bad place to look next.

Timz06

you must be losing a ground if you are not blowing fuses. If you were shorting out a power wire, you would blow a fuse.

I had my harness behind the fuel rail get a small nick in it. It caused the fuse to blow and I lost the right 4 injectors. It was hard to find.

The way I finally found it was to insert my ohm meter in the fuse block for the circuit. I wiggled harnesses until I saw the resistance change. Maybe you could try that for your main circuits.

Tim

exracer28

use a data logger and record voltages at different places in the harness. I like some of the newer strip chart recorders where I can record hi and low side of a dozen points.
Poor mans version is test lights wired to different locations and if light goes off you have a starting point. When checking a connection do not just look for a beep. Look at the numbers.

Kanmer

Check and double check ALL grounds! There are a few critical grounds around the bell housing.

Bob

mgarfias

Something like this happened to my wife's 00 pontiac grand prix. Just mysteriously cut the ignition when driving around. No amount of data logging did any good, as the PCM was losing power. After numerous repair attempts GM bought the car back.

My vote is something in or near the ignition switch. If it was one of the big grounds shorting you'd know. If it was a big wire losing connections intermittently you'd also smell the ozone. Its got to be something small, and that means in the column most likely.

The ignition switch is the only bit that actually moves, so I'd start there.

zrracer

Listen to 96 collector! I have been down this road its the battery!!!!

sothpaw2

Bob,

Can one really examine those without pulling the torque tube etc? Those are the ones I'm worried about that have not been checked yet.

exracer28

the only way to collect data is with a stand alone power source. The equipment I use are all battery powered.

I can't speak for what the GM shop did but I have been doing this for a long time and with todays equipment you have to work at it to lose data. It does not matter if the PCM was losing power the data is stored external to the PCM. It seems strange that if they knew the PCM input power was the issue why they could not then repair the car. As others have pointed out grounds can cause lots of issues. With the car only doing it at VIR under high G conditions a poor ground would be top on my list. Add additional grounds from battery to frame and battery to block. If that corrects issue then remove one and retest. You should be able find issue.

Good luck

John AKA "Sparky"

Kanmer

Yes, they are external.

Bob

PA Z06

I had 2 z06s with a similar problem, dash wouldent shut off, but the car would loose all power. There is a main harness towards the back of the motor near the clutch res, and when the motor would move under heavy tq the harness would stretch and short. Like I said had it happen to 2 z06s, its a simple fix; just insulate the harness and all has been good since.

sothpaw2

What did you have to do to get the harness out? I mentioned this & I think I was told "intake manifold" etc has to come out to get enough access to get that harness out to find where exactly the insulation is damaged.

sothpaw2

John,

What data logger do you recommend that I could hook up & monitor different circuits? Something easy to use? It'd be great if it ran off it's own battery power rather than plug in to the ALDL plug.

Thanks

Andy